Exercise weight stacks are well known in the art and prevalent in the exercise equipment industry. Generally speaking, a plurality of weights or plates are arranged in a stack and maintained in alignment by guide members or rods. A desired amount of weight is engaged by selectively connecting a selector rod to the appropriate weight in the stack. The selector rod and/or the uppermost weight in the stack are/is connected to at least one force receiving member by means of a connector. The engaged weight is lifted up from the stack in response to movement of the force receiving member.
Some examples of conventional weight stacks, their applications, and/or features are disclosed in U.S. Pat. No. 3,912,261 to Lambert, Sr. (shows an exercise machine which provides weight stack resistance to a single exercise motion); U.S. Pat. No. 5,263,915 to Habing (shows an exercise machine which uses a single weight stack to provide resistance to several different exercise motions); U.S. Pat. No. 4,900,018 to Ish III, et al. (shows an exercise machine which provides weight stack resistance to a variety of exercise motions); U.S. Pat. No. 4,878,663 to Luquette (shows an exercise machine which has rigid linkage members interconnected between a weight stack and a force receiving member); U.S. Pat. No. 4,601,466 to Lais (shows bushings which are attached to weight stack plates to facilitate movement along conventional guide rods); U.S. Pat. No. 5,374,229 to Sencil (shows an alternative to conventional guide rods); U.S. Pat. No. 4,878,662 to Chern (shows a selector rod arrangement for clamping the selected weights together into a collective mass); U.S. Pat. No. 4,809,973 to Johns (shows telescoping safety shields which allow insertion of a selector pin but otherwise enclose the weight stack); U.S. Pat. No. 5,000,446 to Sarno (shows discrete selector pin configurations intended for use on discrete machines); U.S. Pat. No. 4,546,971 to Raasoch (shows levers operable to remotely select a desired number of weights in a stack); U.S. Pat. No. 5,037,089 to Spagnuolo et al. (shows a controller operable to automatically adjust weight stack resistance); U.S. Pat. No. 4,411,424 to Barnett (shows a dual-pronged pin which engages opposite sides of a selector rod); U.S. Pat. No. 1,053,109 to Reach (shows a stack of weight plates, each having a slide which moves into and out of engagement with the weight plate or top plate above it); and U.S. Pat. No. 5,306,221 to Itaru (shows a stack of weight plates, each having a lever which pivots into and out of engagement with a selector rod). Despite these advances and others in the weight stack art, room for improvement and ongoing innovation continues to exist.
Exercise dumbbells are also well known in the art and prevalent in the exercise equipment industry. Generally speaking, each dumbbell includes a handle and a desired number of weights or plates which are secured to opposite sides of the handle. The dumbbell is lifted up subject to gravitational force acting on the mass of the handle and attached weights.
Some examples of adjustable weight dumbbells are disclosed in U.S. Pat. No. 4,529,198 to Hettick, Jr. (shows a barbell assembly having weight plates stored at opposite ends of a base and selectively connected to respective ends of a handle member); and U.S. Pat. No. 5,637,064 to Olson et al. (shows a dumbbell assembly having a plurality of weights stored in nested relationship to one another and selectively connected to a handle member).